This theory would check out if a proprietary vendor could easily get away with shipping a single binary package for all supported versions of, say, Ubuntu.

Having to build and maintain a binary packege separately for each version of the same distro probably isn't that appealing to them.

For Ubuntu they would only target LTS releases, most likely.

On EL it's easier, now you would just support 2 or 3 of EL7, EL8, and EL9.

As an example of something I use, Xfdtd only officially supports one version of Ubuntu and 2 versions of EL https://www.remcom.com/system-requirements#xfdtd-system-requ...

In practice, it wasn't too hard to get it running on EL9 or Fedora either...